Method and device for adjusting the tension of yarn fed to a yarn-consuming machine



June 24, 1969 B. F. HELFFER ETAL 3,451,603

METHOD AND DEVICE FOR ADJUSTING THE TENSION OF YARN FED TO A- YARN-CONSUMING MACHINE Filed May 17. 1966 Sheet of s [and in grams A 1. III cm 52 Luz 5 4L BERNARb-FRANco|s HELFFEIZ,

JEAN-PIERRE A.ENSIN EUGENE J'- V'onsm Wasmfe ATTOZIVEVJ' June 24, 1969 a. F. HELFFER ET AL- 3,451,603

METHOD AND DEVICE FOR ADJUSTING THE TENSION OF YARN FED TO A YARN-GONSUMING MACHINE Filed May 17. 1966 Sheet 2 015 Fig 4? IIIIJHHII I HIHH Hll F Illlllllllllllllll Illllllll lNl/E'lvraej B ERNAQo-FIZANQOIS HELFF-se,

JEAN-PIERRE AJZmsm EUGENE J". VOISIN WM QJLAJ gwi A 7 TOE/VEKS June 24, 1969' B. F. HELFFER ETAL 3,451,603

METHOD AND DEVICE FOR ADJUSTING THE TENSION OF YARN FED TO A YARN-CONSUMING MACHINE 3 Filed May 17. 1966 Sheet 01' 5 //VVE/V7'0/6J BERNARD-FRANCOtS HELFFEE JEAN-PIERRE A-Qmsm i Euesm; I Vonsm ma 55% gwm United States Patent 3,451,603 METHOD AND DEVICE FOR ADJUSTING THE TENSION OF YARN FED TO A YARN-CON- SUMING MACHINE Bernard Francois Hellfer, Saint-Andre-les-Vergers, Jean- Pierre A. Raisin, Troyes, and Eugene J. Voisin, Saint- Andre-les-Vergers, France, assignors to Institut Textile de France, Boulogne-sur-Seine, France Filed May 17, 1966, Ser. No. 550,715 Claims priority, application France, May '18, 1965, 17,408; Mar. 24, 1966, 54,864 Int. Cl. B65h 77/00; D04b /46, 15/50 U.S. Cl. 226-1 2 Claims ABSTRACT OF THE DISCLOSURE Method and device for feeding a high-stretch yarn to a yarn consuming machine at a constant speed and tension comprising supplying the yarn at an uncontrolled tension, imparting to the yarn a constant speed and a tension which is higher than the decrimping tension, then easing the imparted tension so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by the application of the imparted tension so as to achieve a delivery tension which is lower than the decrimping tension but which may be varied without the production of appreciable variation in length of the yarn.

The present invention relates to a yarn feed device and method intended to be used primarily for feeding hosiery knitting or other yarn-consuming machines.

On a knitting machine, the yarn, while passing through a certain number of straddling devices such as yarn guides, yarn breakers, throwers and the like, is fed from the bobbin to the needles without being controlled, at any point in its path, by a device for checking its unwinding speed. Experience shows that the unwinding of the yarn is not uniform, either as between one yarn and another, or as between one portion and another of the same yarn. This is mainly due to the frictional forces to which the yarn is subjected at various points before its reaches the needles. While the yarn is leaving the spool, moreover, the latter is frequently jerked, which also contributes to the creation of undesirable irregularities.

To remedy these difficulties, it has already been proposed that there should be interposed, between the bobbin and the needles of a knitting machine, a yarn feed device with which either the tension or the speed of the thread might be regulated. One such yarn feed device, with which the speed of the yarn can be kept constant, consists of a frusto-conical drum, mounted to rotate about its longitudinal axis, and a yarn guide fixed rigidly to a lever, to the other end of which is fitted a restoring spring that causes the lever to swing, to a certain extent, so that the yarn passing through the guide is wound once or several times round the frusto-conical drum and rises towards the top or falls towards the base of the drum, in order to keep the thread under constant tension. Obviously, with the drum rotating at a particular speed, the speed of the yarn as it leaves the drum varies with the changes in the drum diameter where the yarn is wound on to it.

Another previously suggested yarn feed, which consists likewise of a frusto-conical drum and a yarn guide movable on an axis parallel to one position of the line generating the inclined face of the frusto-conical drum, enables the speed at which the yarn leaves the drum to be kept constant. In this device the yarn is wound once around the drum, to the face of which it adheres strongly, this face generally being made of a material possessing a high coefficient of friction, such as rubber. For any given 3,451,603 Patented June 24, 1969 diameter at which the yarn is wound about the drum, the yarn will leave the drum at a constant speed, that is to say, giving a constant feed but, with this device, one cannot closely control the thread tension in the case of a textured yarn.

With another previously suggested yarn feed device it is possible to eliminate the variations in yarn tension due to variations in the speed of unwind from the bobbin. This feed device comprises a drum to which rotary motion is imparted and which consists of two truncated cones following each other along the axis of the drum and joined by a frusto-conical bevel, associated yarn guides being so placed in relation to the drum that the yarn, during the first part of its path from bobbin to needle, makes contact with "the first truncated cone along an arc of a circle and then, during the second part of its path, firstly with the same truncated cone along a helical path diametrically opposite the circular arc and then with the frusto-conical bevel, the yarn finally making contact, during a third part of its path, with the second truncated cone along a circular are equal to that defined on the first truncated cone by the first part of the path of the yarn. By reason of the particular path followed, the yarn is subjected to a given tension during the first part of this path, to a higher tension during the second part of its path and, finally, in the third part of its path to a tension equal to the first. In general terms, this yarn feed prevents the thread from slipping on the drum.

These previously proposed yarn feed devices, and the methods that can be used with their aid, are more or less well suited to feeding hosiery knitting machines with nontextured, that is to say, low-stretch, threads. However, when yarns likely to stretch considerably, such as textured threads (crimped yarns) are to be used, the previously proposed feed devices and the feeding methods made possible by their use do not enable the yarn tension and speed to be kept constant, because sudden changes in tension beyond the feed device may cause the yarn to slip theron.

High-stretch yarns, such as crimped yarns, elastomers and the like, are known to be characterised by very high variations in stretch for very small changes in loading force. If we look at the load/stretch curve for such a yarn, we find that, in an initial zone which we may call the uncurling, uncrimping, or curl-elongation zone, the variations in stretch for small changes in load are very large. Beyond this zone the variation with load in the stretch of the yarn is very small, even for considerable changes in tension or loading. The length (in other Words, the speed) of a high-stretch yarn could therefore be controlled if the tension applied to it lay beyond the uncurling zone. This means that the tension should be higher than 0.1 gramme/denier, or 0.9 g./tex. Even for a ZOO-denier thread, however, this would make a tension equivalent to a load of 20 g.; and in the case of a textured yarn used in a knitting machine, one cannot knit at such high tensions without running into trouble.

The object of the present invention is to provide a method and feed device whereby yarn consuming machines, and knitting machines in particular, can be fed with high-stretch yarn at substantially constant speed and under substantially constant tension.

According to the present invention there is provided a method of feeding high-stretch yarn to a yarn-consuming machine at constant speed and tension, comprising the steps of supplying the yarn at a high but uncontrolled tension over a first part of its path, imparting to the yarn a constant speed and high tension over a second part of its path, the said high tension being beyond the decrimping tension of the load/stretch curve of the yarn, and easing said high tension in the yarn over a third part of 3 its path so as to achieve a relatively lower delivery tension, the value of which lower tension lies below decrimping tension point of the said curve.

Further, according to the present invention, there is provided a yarn feed device for feeding a high-stretch yarn to a yarn-consuming machine at a constant speed and tension, said device comprising means for supplying the yarn at a high but uncontrolled tension over a first part of its path, means for imparting to the yarn a constant speed and a high tension over a second part of its path, the said high tension being beyond the decrimping tension of the load/stretch curve of the yarn, and means for casing in the yarn said high tension over a third part of its path so as to achieve a relatively lower delivery tension, the value of which lower tension lies below the decrirnping tension of the said curve.

The term decrimping tension when used herein means the tension required to remove substantially all of the crimping from a given yarn.

For knitting adjoining edges or heel reinforcements, the yarn feed device mentioned above requires the yarn to be removed from the various yarn guides, which always involves stopping the machines for an appreciable time. This drawback becomes particularly manifest where knitting is not continuous; such as in the case ef machines for forming continuous edge ribs or stocking knitting machines.

As is well known, machines for forming continuous edge ribs knit panels joined by the edges of the ribs and the changes in tension that may result from this require the thread feed to be disconnected. The same applies to the making of stockings, more particularly at the transition from continuous rotary movement to alternating rotary movement for knitting the heel reinforcement.

The present invention also relates to a yarn feed device which enables the knitting machine with which it is associated to pass readily and without waste of time from continuous to non-continuous knitting and to restore tension under these conditions.

For this purpose, in a yarn feed device with two drums rotating at difierent peripheral speeds, at least the delivery drum of the yarn feed device is fitted with a member, which can be moved clear, the purpose of which is to hold the yarn against and to prevent it from slipping on part of the periphery of the delivery drum.

Certain embodiments of yarn-tensioning devices in accordance with the present invention will now be described by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a graph of the load/ stretch curve illustrating hysteresis of a textured thread, for example, Helanca-IOO-d (registered trademark);

FIGURE 2 is a plan view showing a first embodiment of a thread feed device in accordance with the invention;

FIGURE 3 is an end elevation of the feed device of FIGURE 2;

FIGURE 4 is an end elevation of a second embodiment of the feed device; and

FIGURE 5 is an end elevation of a third embodiment feed device.

In the graph in FIGURE 1, the abscissae represent the loading in grammes applied to a textured thread (crimped yarn) of given initial length 0.50 m., the ordinates representing the stretch (L) in centimetres corresponding to a given loading. High-stretch yarns such as crimped yarn, elastomer filaments and the like are known to be characterised by very high variations in stretch for small changes in loading. If the load/stretch curve R of such a yarn is considered, it will be observed for a zone lying between the origin 0 and the point H, which may be called the uncrimping or crimping elongation curve, that the variations in the stretch of the yarn are clearly larger than for equal changes in the loading to which it is subjected beyond this zone, that is to say, above the point H, where an increase in the yarn loading results in only slight further elongation. In fact, from curve R, it will be seen that, for one and the same load variation, AC, the stretch variation AL obtained in uncrimping zone OH is far larger than the stretch variation AL obtained in that part of the curve which lies beyond point H. This means that it is possible to control the length of yarn taken only when the tension applied to it is equal to or greater than the value H, which is approximately 0.1 g./ denier. It must be recognised, however, that this represents, for a ZOO-denier yarn, a load of 20 grammes, and that one cannot knit at such high tensions Without encountering difiiculties. If the load on the yarn be first increased to a value K and then reduced, the resulting curve S lies above the curve R and shows a given hysteresis, so that one can reduce the yarn tension to values substantially lower than value H without thereby affecting the length of yarn delivered, that is to say, without the yarn undergoing any considerable reduction in length.

The yarn feed devices in accordance with the invention serve to apply the results of this experiment.

In one advantageous form, the device comprises two frusto-conical drums A and B, of suitable dimensions for covering the entire range of tightness of the knitting or other yarn-consuming machines. These two drums may be identical to or differently shaped from each other. In one such pair of drums A and B (as illustrated), they are situated side by side with their axes parallel and are covered with a facing having a high co-efficient of friction to prevent the yarn from slipping. This facing may, for example, be made of rubber. On the base of each of the frustoconical drums is mounted a pinion, the pinion spindles being journalled in suitable bearings (not shown). A gearwheel mounted between the two drums meshes with each of the drum pinions. These two drums are mechanically driven from a motor (not shown) through the said gearwheel and may each rotate at the same speed and in the same direction. It would be equally possible to drive the drums in opposite directions and at diiferent speeds. Each driving drum A and B is associated with a take-up yarn guide 1 and 3 respectively, and a delivery yarn guide 2 and 4 respectively. Take-up yarn guides 1 and 3 and delivery yarn guides 2 and 4 are rigidly attached to runners 5 and 6 respectively, mounted on a worm thread 7 and 8 respectively, along which they can move axially. A separate guide rod (not shown) passes through each runner 5 and 6 in order to prevent its rotation about thread 7 or 8. Each worm thread lies near the corresponding frusto-conical drum and parallel to a line generating the sloping face thereof or to the axis thereof. By rotating the thread 7 or 8, it is possible to obtain the desired independent positioning of each runner, with its take-up yarn guide and delivery yarn guide, in relation to the frustum height of the corresponding drum A or B. Yarn F arriving at an uncontrolled speed and tension from a supply bobbin (not shown), passes through the take-up yarn guide 1 of the first drum A, passes once completely around this drum and through the delivery thread guide 2. and is then led, to the take-up yarn guide 3 of the second drum B. The yarn then passes once completely around the drum B and on through the delivery yarn guide 4, before being taken to the knocking-down cam and from there to the needles.

Each drum A and B enables yarn to be delivered at a given constant speed for a given speed of rotation, which is the same for each drum, the speed of delivery of the yarn from each drum being determined by the diameter of that section of the drum around which the yarn is Wound. Three cases can arise: the yarn delivery speed of the drum A is lower than the yarn delivery speed of the drum B; or the delivery speed from drum A is equal to that from the drum B; or the delivery speed from the drum A is higher than that from the drum B. It is only the first of these cases with which this embodiment is concerned. If the position of the yarn guides 3 and 4 at the drum B is so adjusted that the yarn is delivered from the drum A at a lower speed than from the drum B, stretching of that part of the yarn which lies between the two drums will take place, i.e., a first part of its path, so that the tension on this part of the yarn will be increased. This yarn tension between the two drums will be termed the intermediate tension T Preferably the intermediate tension is up to times higher than the tension at delivery.

The positioning of the runner 6, with its yarn guides 3 and 4, makes it possible, after passing partly around the drum B, which constitutes a second part of its path, to obtain from the second drum the yarn delivery speed at a third part of its path requisite for the desired length of stitch. The positioning of the runner 5, with its yarn guides 1 and 2, enables the speed of delivery of the yarn from the first drum A, to be so determined as to produce the correct intermediate tension T between the drums A and B. The take-up speed T of the yarn F prior to its admission to the feed device at the yarn guide 1 may vary and may be of any value. The delivery tension T of the yarn F after its passage through the feed device and between this and the yarn-consuming machine (that is to say, in the case of a knitting machine, the needles), is regulated to the desired value by suitable positioning of the knocking-down cam of the knitting machine (not shown).

Thus, with the aid of a feed device hereinbefore particularly described, it is possible to use a method of feeding high-stretch yarn to a hosiery knitting or other yamconsuming machine at constant speed and tension; the tension at which the yarn reaches the machine remaining low, this method comprising the steps of subjecting the yarn to tension which is higher than the decrimping tension, such as to bring it into a load/ stretch zone in which variations in the loading applied to the yarn do not result in appreciable stretching, and then in reducing the tension in accordance with the hysteresis characteristic, whereby a considerable reduction in loading does not produce appreciable variation in the length of the yarn; so that the yarn delivery and the low tension on the yarn reaching the yarn-consuming machine (and, more particularly, the needles of a knitting machine) remain strictly constant, irrespective of the speed and tension at which the yarn is taken up by the feed device.

Instead of frusto-conical drums rotating at equal peripheral speeds and winding the same yarn, of which the loop around the first drum is smaller in diameter than the loop round the second drum, it is possible to employ cylindrical drums, the first rotating at a lower peripheral speed than the second. The feed device can be used not only with a hosiery knitting machine, but can also be applied to any machine or mechanism which requires yarn at a strictly controlled speed and tension.

A yarn feed device shown in FIGURES 4 and 5 has two cylindrical driving drums 11 and 12 spaced apart from each other.

In general terms, the take-up drum 11 turns at a lower peripheral speed than the delivery drum 12. The drums 11 and 12 may be driven by a single motor, a variable speed gear box (not shown) being interposed between the two drums to provide any desired differences in the peripheral speeds.

In the second embodiment shown in FIGURE 4, the delivery drum 12 is provided with a device 13 for holding the yarn in engagement with part of the surface of the drum 12. This device 13 consists of two rollers 14 and 15, spaced apart from each other and mounted on one and the same support (not shown). This support is adjustable and enables the rollers 14 and 15 to be brought towards or moved away from the drum 12. The two rollers 14 and 15 carry an endless belt 16, which, like the drum 12, has a high coefiicient of friction. The endless belt is driven either by one of the rollers 14 and 15 or by the drum 12.

The yarn F, in this case, passes around the first drum 11, without the friction force necessarily being the same between the starting up and the normal running of the feed device. After passing once completely around the first or braking drum 11, yarn F is applied against part of the face of the drum 12 by the endless belt of the device 13. Hence, the yarn F moves at the same speed as any point on the periphery of the drum 12. Since the peripheral speed of the drum 12 is higher than that of the drum 11, yarn F undergoes stretching while passing between these two drums, accompanied by the intermediate tension hereinbefore referred to.

For the knitting of adjoining edges or heel reinforcements, the device 13 is moved clear of the drum 12. By reason of its being wound around the drum 11, the yarn F is still well controlled as regards tension.

In the third embodiment shown in FIGURE 5, the take-up drurn 11 in the yarn-feed device is likewise provived with a device 13- for holding the yarn in engagement with the drum 11, which is the same as the device 13 on the other drum 12 (FIGURE 4 or 5). The components of the device 13 are identical to those of the device 13 and have therefore been numbered similarly, with the addition of a prime. The yarn F is thus firmly held against both drums 11 and 12 and is bound to move at speeds equal to the peripheral speeds of the two drums. Because of the difference in speed between the first drum and the second, the yarn F is subjected to tension between drums 11 and 12. To free the yarn F, all that is required is to move devices 13 and 13 away from drums 11 and 12. It is equally possible, of course, for these devices 13 and 13' to be stationary and for drums 11 and 12 to be adjustable in relation to them.

We claim:

1. A method of feeding high stretch yarn to a hosieryknitting or other yarn-consuming machine at constant speed and tension comprising the steps of supplying the yarn at an uncontrolled tension, imparting to the yarn over a first part of its path a constant speed and a tension which is higher than the decrimping tension, and easing the said imparted tension over a second part of its path so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by the application of said imparted tension such that at a third part of its path a delivery tension is achieved which is lower than the decrimping tension whilst permitting a variation of tension to be tolerated without the production of appreciable variation in length of the yarn.

2. A method according to claim 1, wherein the tension applied over the first part of the path is up to ten times higher than the tension imparted in the third part of the path.

References Cited UNITED STATES PATENTS 2,410,419 11/1946 Bellezza 2424'7.09 3,099,143 7/1963 Sinclair 66-132 3,112,054 11/ 1963 Fleissner 226-172 X 3,184,820 5/1965 Kanbar 2871.3

FOREIGN PATENTS 324,785 2/1930 Great Britain.

EDWARD A. SROKA, Primary Examiner.

U.S. Cl. X.R. 

